Distribution of Anopheles quadrimaculatus and An. crucians larvae within rice field habitats in southwestern Louisiana.

This study, conducted in 3 parishes of Louisiana, documented the distribution pattern of Anopheles quadrimaculatus and An. crucians during the first crop season. Ratios of numbers of 3rd and 4th instar larvae of An. quadrimaculatus to the number of An. crucians 3rd and 4th instar larvae (Q/C), varied both spatially and temporally. The mean Q/C ratio during 1984 was 1.37; during 1985 it was 1.40. The ratios changed from week to week during each year, and increases or decreases in a particular week of 1984 were paralleled by increases or decreases during that same week of 1985. The changes in relative abundance of the 2 species were strongly related to the timing of irrigation practices and to a succession of habitat conditions. Anopheles quadrimaculatus larvae were dominant or exclusively present for several days after fresh water was added to the field. Anopheles crucians larvae then became dominant or exclusively present as the habitat progressed towards a eutrophic condition. Irrigation influenced the conditions of the habitat by freshening and deepening the water, causing a reversion towards a more oligotrophic condition.

The sequential sampling of Psorophora columbiae larvae in rice fields.

Sequential sampling plans were developed for larval populations of Psorophora columbiae developing in rice fields during the growth of rice for a 2nd crop in southwestern Louisiana. Two types of plans were developed: 1) sequential counting plans to estimate the true mean of a population with a prespecified coefficient of variation and 2) sequential decision plans to assist in deciding whether the mean larval count/dip lies outside preselected upper or lower levels. The procedure by which the plans were developed consisted of: 1) conventional larval sampling by dipping along rice field levees that divided each field into pans; 2) counting the number of 2nd through 4th instar larvae observed in two dips taken at each sampling location; and 3) determination of the appropriate statistical parameters from which probability curves, number of samples required, and cumulative larval totals for specific sampling plans could be derived. Both sequential sampling plans are based upon distributions attendant to naturally occurring populations.

Improved caging for nine-banded armadillos.

Impact resistant polyethylene cages were evaluated in these laboratories as replacements for plywood boxes for housing nine-banded armadillos. They were found to be less expensive, easier to sanitize, and to require less than one-third as much floor space per animal as the boxes. This innovation has made it practical to house large numbers of armadillos economically and conveniently in almost any animal facility.